import torch
from collections import deque
import typing as tp
import math
import torch
import torch.nn as nn
from torch.nn.modules.rnn import LSTM
from torch.nn import Module, ModuleList
from einops import rearrange, pack, unpack, reduce, repeat
from einops.layers.torch import Rearrange
import torch.nn.functional as F
from models.bs_roformer.attend import Attend
from rotary_embedding_torch import RotaryEmbedding


# helper functions

def exists(val):
    return val is not None


def default(v, d):
    return v if exists(v) else d


def pack_one(t, pattern):
    return pack([t], pattern)


def unpack_one(t, ps, pattern):
    return unpack(t, ps, pattern)[0]


def pad_at_dim(t, pad, dim=-1, value=0.):
    dims_from_right = (- dim - 1) if dim < 0 else (t.ndim - dim - 1)
    zeros = ((0, 0) * dims_from_right)
    return F.pad(t, (*zeros, *pad), value=value)


def l2norm(t):
    return F.normalize(t, dim=-1, p=2)


# norm

class RMSNorm(Module):
    def __init__(self, dim):
        super().__init__()
        self.scale = dim ** 0.5
        self.gamma = nn.Parameter(torch.ones(dim))

    def forward(self, x):
        return F.normalize(x, dim=-1) * self.scale * self.gamma


# attention

class FeedForward(Module):
    def __init__(
            self,
            dim,
            mult=4,
            dropout=0.
    ):
        super().__init__()
        dim_inner = int(dim * mult)
        self.net = nn.Sequential(
            RMSNorm(dim),
            nn.Linear(dim, dim_inner),
            nn.GELU(),
            nn.Dropout(dropout),
            nn.Linear(dim_inner, dim),
            nn.Dropout(dropout)
        )

    def forward(self, x):
        return self.net(x)


class Attention(Module):
    def __init__(
            self,
            dim,
            heads=8,
            dim_head=64,
            dropout=0.,
            rotary_embed=None,
            flash=True
    ):
        super().__init__()
        self.heads = heads
        self.scale = dim_head ** -0.5
        dim_inner = heads * dim_head

        self.rotary_embed = rotary_embed

        self.attend = Attend(flash=flash, dropout=dropout)

        self.norm = RMSNorm(dim)
        self.to_qkv = nn.Linear(dim, dim_inner * 3, bias=False)

        self.to_gates = nn.Linear(dim, heads)

        self.to_out = nn.Sequential(
            nn.Linear(dim_inner, dim, bias=False),
            nn.Dropout(dropout)
        )

    def forward(self, x):
        x = self.norm(x)

        q, k, v = rearrange(self.to_qkv(x), 'b n (qkv h d) -> qkv b h n d', qkv=3, h=self.heads)

        if exists(self.rotary_embed):
            q = self.rotary_embed.rotate_queries_or_keys(q)
            k = self.rotary_embed.rotate_queries_or_keys(k)

        out = self.attend(q, k, v)

        gates = self.to_gates(x)
        out = out * rearrange(gates, 'b n h -> b h n 1').sigmoid()

        out = rearrange(out, 'b h n d -> b n (h d)')
        return self.to_out(out)


class Transformer(Module):
    def __init__(
            self,
            *,
            dim,
            depth,
            dim_head=64,
            heads=8,
            attn_dropout=0.,
            ff_dropout=0.,
            ff_mult=4,
            norm_output=True,
            rotary_embed=None,
            flash_attn=True,
            linear_attn=False
    ):
        super().__init__()
        self.layers = ModuleList([])

        for _ in range(depth):
            attn = Attention(dim=dim, dim_head=dim_head, heads=heads, dropout=attn_dropout, rotary_embed=rotary_embed, flash=flash_attn)

            self.layers.append(ModuleList([
                attn,
                FeedForward(dim=dim, mult=ff_mult, dropout=ff_dropout)
            ]))

        self.norm = RMSNorm(dim) if norm_output else nn.Identity()

    def forward(self, x):

        for attn, ff in self.layers:
            x = attn(x) + x
            x = ff(x) + x

        return self.norm(x)


class FeatureConversion(nn.Module):
    """
    Integrates into the adjacent Dual-Path layer.

    Args:
        channels (int): Number of input channels.
        inverse (bool): If True, uses ifft; otherwise, uses rfft.
    """

    def __init__(self, channels, inverse):
        super().__init__()
        self.inverse = inverse
        self.channels = channels

    def forward(self, x):
        # B, C, F, T = x.shape
        if self.inverse:
            x = x.float()
            x_r = x[:, :self.channels // 2, :, :]
            x_i = x[:, self.channels // 2:, :, :]
            x = torch.complex(x_r, x_i)
            x = torch.fft.irfft(x, dim=3, norm="ortho")
        else:
            x = x.float()
            x = torch.fft.rfft(x, dim=3, norm="ortho")
            x_real = x.real
            x_imag = x.imag
            x = torch.cat([x_real, x_imag], dim=1)
        return x


class DualPathTran(nn.Module):
    """
    Dual-Path Transformer in Separation Network.

    Args:
        d_model (int): The number of expected features in the input (input_size).
        expand (int): Expansion factor used to calculate the hidden_size of LSTM.
        bidirectional (bool): If True, becomes a bidirectional LSTM.
    """

    def __init__(self, d_model, time_rotary_embed, freq_rotary_embed, tran_params):
        super(DualPathTran, self).__init__()

        self.d_model = d_model

        transformer_kwargs = dict(
            dim=d_model,
            heads=tran_params['heads'],
            dim_head=tran_params['dim_head'],
            attn_dropout=tran_params['attn_dropout'],
            ff_dropout=tran_params['ff_dropout'],
            flash_attn=tran_params['flash_attn']
        )
        self.norm_layers = nn.ModuleList([nn.GroupNorm(1, d_model) for _ in range(2)])
        self.time_layer = Transformer(depth=tran_params['depth'], rotary_embed=time_rotary_embed, **transformer_kwargs)
        self.freq_layer = Transformer(depth=tran_params['depth'], rotary_embed=freq_rotary_embed, **transformer_kwargs)

    def forward(self, x):
        B, C, F, T = x.shape

        # Process dual-path rnn
        original_x = x
        # Frequency-path
        x = self.norm_layers[0](x)
        x = x.transpose(1, 3).contiguous().view(B * T, F, C)
        # print('XXX', x.shape)
        x = self.freq_layer(x)
        x = x.view(B, T, F, C).transpose(1, 3)
        x = x + original_x

        original_x = x
        # Time-path
        x = self.norm_layers[1](x)
        x = x.transpose(1, 2).contiguous().view(B * F, C, T).transpose(1, 2)
        # print('RRR', x.shape)
        x = self.time_layer(x)
        x = x.transpose(1, 2).contiguous().view(B, F, C, T).transpose(1, 2)
        x = x + original_x

        return x


class SeparationNetTran(nn.Module):
    """
    Implements a simplified Sparse Down-sample block in an encoder architecture.

    Args:
    - channels (int): Number input channels.
    - expand (int): Expansion factor used to calculate the hidden_size of LSTM.
    - num_layers (int): Number of dual-path layers.
    """

    def __init__(self, channels, expand=1, num_layers=6, tran_params=None):
        super(SeparationNetTran, self).__init__()

        self.num_layers = num_layers

        time_rotary_embed = RotaryEmbedding(dim=tran_params['rotary_embedding_dim'])
        freq_rotary_embed = RotaryEmbedding(dim=tran_params['rotary_embedding_dim'])

        modules = []
        for i in range(num_layers):
            m = DualPathTran(channels * (2 if i % 2 == 1 else 1), time_rotary_embed, freq_rotary_embed, tran_params)
            modules.append(m)
        self.dp_modules = nn.ModuleList(modules)

        self.feature_conversion = nn.ModuleList([
            FeatureConversion(channels * 2, inverse=False if i % 2 == 0 else True) for i in range(num_layers)
        ])

    def forward(self, x):
        for i in range(self.num_layers):
            x = self.dp_modules[i](x)
            x = self.feature_conversion[i](x)
        return x


class Swish(nn.Module):
    def forward(self, x):
        return x * x.sigmoid()


class ConvolutionModule(nn.Module):
    """
    Convolution Module in SD block.

    Args:
        channels (int): input/output channels.
        depth (int): number of layers in the residual branch. Each layer has its own
        compress (float): amount of channel compression.
        kernel (int): kernel size for the convolutions.
        """

    def __init__(self, channels, depth=2, compress=4, kernel=3):
        super().__init__()
        assert kernel % 2 == 1
        self.depth = abs(depth)
        hidden_size = int(channels / compress)
        norm = lambda d: nn.GroupNorm(1, d)
        self.layers = nn.ModuleList([])
        for _ in range(self.depth):
            padding = (kernel // 2)
            mods = [
                norm(channels),
                nn.Conv1d(channels, hidden_size * 2, kernel, padding=padding),
                nn.GLU(1),
                nn.Conv1d(hidden_size, hidden_size, kernel, padding=padding, groups=hidden_size),
                norm(hidden_size),
                Swish(),
                nn.Conv1d(hidden_size, channels, 1),
            ]
            layer = nn.Sequential(*mods)
            self.layers.append(layer)

    def forward(self, x):
        for layer in self.layers:
            x = x + layer(x)
        return x


class FusionLayer(nn.Module):
    """
    A FusionLayer within the decoder.

    Args:
    - channels (int): Number of input channels.
    - kernel_size (int, optional): Kernel size for the convolutional layer, defaults to 3.
    - stride (int, optional): Stride for the convolutional layer, defaults to 1.
    - padding (int, optional): Padding for the convolutional layer, defaults to 1.
    """

    def __init__(self, channels, kernel_size=3, stride=1, padding=1):
        super(FusionLayer, self).__init__()
        self.conv = nn.Conv2d(channels * 2, channels * 2, kernel_size, stride=stride, padding=padding)

    def forward(self, x, skip=None):
        if skip is not None:
            x += skip
        x = x.repeat(1, 2, 1, 1)
        x = self.conv(x)
        x = F.glu(x, dim=1)
        return x


class SDlayer(nn.Module):
    """
    Implements a Sparse Down-sample Layer for processing different frequency bands separately.

    Args:
    - channels_in (int): Input channel count.
    - channels_out (int): Output channel count.
    - band_configs (dict): A dictionary containing configuration for each frequency band.
                           Keys are 'low', 'mid', 'high' for each band, and values are
                           dictionaries with keys 'SR', 'stride', and 'kernel' for proportion,
                           stride, and kernel size, respectively.
    """

    def __init__(self, channels_in, channels_out, band_configs):
        super(SDlayer, self).__init__()

        # Initializing convolutional layers for each band
        self.convs = nn.ModuleList()
        self.strides = []
        self.kernels = []
        for config in band_configs.values():
            self.convs.append(
                nn.Conv2d(channels_in, channels_out, (config['kernel'], 1), (config['stride'], 1), (0, 0)))
            self.strides.append(config['stride'])
            self.kernels.append(config['kernel'])

        # Saving rate proportions for determining splits
        self.SR_low = band_configs['low']['SR']
        self.SR_mid = band_configs['mid']['SR']

    def forward(self, x):
        B, C, Fr, T = x.shape
        # Define splitting points based on sampling rates
        splits = [
            (0, math.ceil(Fr * self.SR_low)),
            (math.ceil(Fr * self.SR_low), math.ceil(Fr * (self.SR_low + self.SR_mid))),
            (math.ceil(Fr * (self.SR_low + self.SR_mid)), Fr)
        ]

        # Processing each band with the corresponding convolution
        outputs = []
        original_lengths = []
        for conv, stride, kernel, (start, end) in zip(self.convs, self.strides, self.kernels, splits):
            extracted = x[:, :, start:end, :]
            original_lengths.append(end - start)
            current_length = extracted.shape[2]

            # padding
            if stride == 1:
                total_padding = kernel - stride
            else:
                total_padding = (stride - current_length % stride) % stride
            pad_left = total_padding // 2
            pad_right = total_padding - pad_left

            padded = F.pad(extracted, (0, 0, pad_left, pad_right))

            output = conv(padded)
            outputs.append(output)

        return outputs, original_lengths


class SUlayer(nn.Module):
    """
    Implements a Sparse Up-sample Layer in decoder.

    Args:
    - channels_in: The number of input channels.
    - channels_out: The number of output channels.
    - convtr_configs: Dictionary containing the configurations for transposed convolutions.
    """

    def __init__(self, channels_in, channels_out, band_configs):
        super(SUlayer, self).__init__()

        # Initializing convolutional layers for each band
        self.convtrs = nn.ModuleList([
            nn.ConvTranspose2d(channels_in, channels_out, [config['kernel'], 1], [config['stride'], 1])
            for _, config in band_configs.items()
        ])

    def forward(self, x, lengths, origin_lengths):
        B, C, Fr, T = x.shape
        # Define splitting points based on input lengths
        splits = [
            (0, lengths[0]),
            (lengths[0], lengths[0] + lengths[1]),
            (lengths[0] + lengths[1], None)
        ]
        # Processing each band with the corresponding convolution
        outputs = []
        for idx, (convtr, (start, end)) in enumerate(zip(self.convtrs, splits)):
            out = convtr(x[:, :, start:end, :])
            # Calculate the distance to trim the output symmetrically to original length
            current_Fr_length = out.shape[2]
            dist = abs(origin_lengths[idx] - current_Fr_length) // 2

            # Trim the output to the original length symmetrically
            trimmed_out = out[:, :, dist:dist + origin_lengths[idx], :]

            outputs.append(trimmed_out)

        # Concatenate trimmed outputs along the frequency dimension to return the final tensor
        x = torch.cat(outputs, dim=2)

        return x


class SDblock(nn.Module):
    """
    Implements a simplified Sparse Down-sample block in encoder.

    Args:
    - channels_in (int): Number of input channels.
    - channels_out (int): Number of output channels.
    - band_config (dict): Configuration for the SDlayer specifying band splits and convolutions.
    - conv_config (dict): Configuration for convolution modules applied to each band.
    - depths (list of int): List specifying the convolution depths for low, mid, and high frequency bands.
    """

    def __init__(self, channels_in, channels_out, band_configs={}, conv_config={}, depths=[3, 2, 1], kernel_size=3):
        super(SDblock, self).__init__()
        self.SDlayer = SDlayer(channels_in, channels_out, band_configs)

        # Dynamically create convolution modules for each band based on depths
        self.conv_modules = nn.ModuleList([
            ConvolutionModule(channels_out, depth, **conv_config) for depth in depths
        ])
        # Set the kernel_size to an odd number.
        self.globalconv = nn.Conv2d(channels_out, channels_out, kernel_size, 1, (kernel_size - 1) // 2)

    def forward(self, x):
        bands, original_lengths = self.SDlayer(x)
        # B, C, f, T = band.shape
        bands = [
            F.gelu(
                conv(band.permute(0, 2, 1, 3).reshape(-1, band.shape[1], band.shape[3]))
                .view(band.shape[0], band.shape[2], band.shape[1], band.shape[3])
                .permute(0, 2, 1, 3)
            )
            for conv, band in zip(self.conv_modules, bands)

        ]
        lengths = [band.size(-2) for band in bands]
        full_band = torch.cat(bands, dim=2)
        skip = full_band

        output = self.globalconv(full_band)

        return output, skip, lengths, original_lengths


class SCNet_Tran(nn.Module):
    """
    The implementation of SCNet: Sparse Compression Network for Music Source Separation. Paper: https://arxiv.org/abs/2401.13276.pdf
    LSTM layers replaced with transformer layers

    Args:
    - sources (List[str]): List of sources to be separated.
    - audio_channels (int): Number of audio channels.
    - nfft (int): Number of FFTs to determine the frequency dimension of the input.
    - hop_size (int): Hop size for the STFT.
    - win_size (int): Window size for STFT.
    - normalized (bool): Whether to normalize the STFT.
    - dims (List[int]): List of channel dimensions for each block.
    - band_SR (List[float]): The proportion of each frequency band.
    - band_stride (List[int]): The down-sampling ratio of each frequency band.
    - band_kernel (List[int]): The kernel sizes for down-sampling convolution in each frequency band
    - conv_depths (List[int]): List specifying the number of convolution modules in each SD block.
    - compress (int): Compression factor for convolution module.
    - conv_kernel (int): Kernel size for convolution layer in convolution module.
    - num_dplayer (int): Number of dual-path layers.
    - expand (int): Expansion factor in the dual-path RNN, default is 1.

    """

    def __init__(
            self,
            sources=('drums', 'bass', 'other', 'vocals'),
            audio_channels=2,
            # Main structure
            dims=(4, 32, 64, 128),  # dims = [4, 64, 128, 256] in SCNet-large
            # STFT
            nfft=4096,
            hop_size=1024,
            win_size=4096,
            normalized=True,
            # SD/SU layer
            band_SR=(0.175, 0.392, 0.433),
            band_stride=(1, 4, 16),
            band_kernel=(3, 4, 16),
            # Convolution Module
            conv_depths=(3, 2, 1),
            compress=4,
            conv_kernel=3,
            # Dual-path RNN
            num_dplayer=6,
            expand=1,
            tran_rotary_embedding_dim=64,
            tran_depth=1,
            tran_heads=8,
            tran_dim_head=64,
            tran_attn_dropout=0.0,
            tran_ff_dropout=0.0,
            tran_flash_attn=False,
    ):
        super().__init__()
        self.sources = sources
        self.audio_channels = audio_channels
        self.dims = dims
        band_keys = ['low', 'mid', 'high']
        self.band_configs = {band_keys[i]: {'SR': band_SR[i], 'stride': band_stride[i], 'kernel': band_kernel[i]} for i
                             in range(len(band_keys))}
        self.hop_length = hop_size
        self.conv_config = {
            'compress': compress,
            'kernel': conv_kernel,
        }
        self.tran_params = {
            'rotary_embedding_dim': tran_rotary_embedding_dim,
            'depth': tran_depth,
            'heads': tran_heads,
            'dim_head': tran_dim_head,
            'attn_dropout': tran_attn_dropout,
            'ff_dropout': tran_ff_dropout,
            'flash_attn': tran_flash_attn,
        }

        self.stft_config = {
            'n_fft': nfft,
            'hop_length': hop_size,
            'win_length': win_size,
            'center': True,
            'normalized': normalized
        }

        self.first_conv = nn.Conv2d(dims[0], dims[0], 1, 1, 0, bias=False)

        self.encoder = nn.ModuleList()
        self.decoder = nn.ModuleList()

        for index in range(len(dims) - 1):
            enc = SDblock(
                channels_in=dims[index],
                channels_out=dims[index + 1],
                band_configs=self.band_configs,
                conv_config=self.conv_config,
                depths=conv_depths
            )
            self.encoder.append(enc)

            dec = nn.Sequential(
                FusionLayer(channels=dims[index + 1]),
                SUlayer(
                    channels_in=dims[index + 1],
                    channels_out=dims[index] if index != 0 else dims[index] * len(sources),
                    band_configs=self.band_configs,
                )
            )
            self.decoder.insert(0, dec)

        self.separation_net = SeparationNetTran(
            channels=dims[-1],
            expand=expand,
            num_layers=num_dplayer,
            tran_params=self.tran_params
        )

    def forward(self, x):
        # B, C, L = x.shape
        B = x.shape[0]
        # In the initial padding, ensure that the number of frames after the STFT (the length of the T dimension) is even,
        # so that the RFFT operation can be used in the separation network.
        padding = self.hop_length - x.shape[-1] % self.hop_length
        if (x.shape[-1] + padding) // self.hop_length % 2 == 0:
            padding += self.hop_length
        x = F.pad(x, (0, padding))

        # STFT
        L = x.shape[-1]
        x = x.reshape(-1, L)
        x = torch.stft(x, **self.stft_config, return_complex=True)
        x = torch.view_as_real(x)
        x = x.permute(0, 3, 1, 2).reshape(x.shape[0] // self.audio_channels, x.shape[3] * self.audio_channels,
                                          x.shape[1], x.shape[2])

        B, C, Fr, T = x.shape

        save_skip = deque()
        save_lengths = deque()
        save_original_lengths = deque()
        # encoder
        for sd_layer in self.encoder:
            x, skip, lengths, original_lengths = sd_layer(x)
            save_skip.append(skip)
            save_lengths.append(lengths)
            save_original_lengths.append(original_lengths)

        # separation
        x = self.separation_net(x)

        # decoder
        for fusion_layer, su_layer in self.decoder:
            x = fusion_layer(x, save_skip.pop())
            x = su_layer(x, save_lengths.pop(), save_original_lengths.pop())

        # output
        n = self.dims[0]
        x = x.view(B, n, -1, Fr, T)

        x = x.reshape(-1, 2, Fr, T).permute(0, 2, 3, 1)
        x = torch.view_as_complex(x.contiguous())
        x = torch.istft(x, **self.stft_config)
        x = x.reshape(B, len(self.sources), self.audio_channels, -1)

        x = x[:, :, :, :-padding]

        return x
